Field of the Invention
The present invention relates to an apparatus for manufacturing tyres for vehicle wheels.
The invention also relates to a process for manufacturing a lot of tyres for vehicle wheels comprising at least two tyres of different radial dimensions.
Description of the Related Art
A tyre for vehicle wheel generally comprises a carcass structure comprising at least one carcass ply formed by reinforcing cords embedded in an elastorneric matrix. The carcass ply has end edges respectively engaged with annular anchoring structures. The latter are arranged in the tyre zones usually identified with the name of “beads” and normally consist each of an annular substantially circumferential insert on which at least one filling insert is applied, in a radially outer position thereof. Such annular anchoring structures are commonly identified as “bead cores” and have the task of keeping the tyre well fixed to the anchoring seat specifically provided in the wheel rim, thus preventing, in operation, the radially inner edge (also referred to as an “end edge” herein) of the tyre coming out from such seat.
At the beads specific reinforcing structures may be provided having the function of improving the torque transmission to the tyre.
In a radially outer position with respect to the carcass ply, a belt structure comprising one or more belt layers is associated, said belt layers being arranged radially one of top of the other and having textile or metal reinforcing cords with crossed orientation and/or substantially parallel to the direction of circumferential extension of the tyre.
Between the carcass structure and the belt structure a layer of elastomeric material, known as “under-belt”, can be provided, said layer having the function of making the radially outer surface of the carcass structure as uniform as possible for the subsequent application of the belt structure.
In a radially outer position with respect to the belt structure a tread band is applied, made from elastomeric material as well.
Between the tread band and the belt structure a so-called “under-layer” of elastomeric material can be arranged, said layer having properties suitable to ensure a steady union of the tread band itself.
On the side surfaces of the carcass structure respective sidewalls of elastomeric material are also applied, each one extending from one of the side edges of the tread band up to the respective annular anchoring structure to the beads. An apparatus for manufacturing the aforementioned carcass structure typically comprises a forming support extending along a longitudinal axis, wherein the above carcass ply is laid on a device for positioning the bead core on the end edge of the carcass ply and a device for turning up the end edge of the carcass ply about the bead core.
The device for positioning the bead core essentially comprises a ring structure axially movable towards the forming support for positioning the bead core on the end edge of the carcass ply and away from the forming support for allowing the execution of the subsequent steps of the tyre bead forming process.
WO 2008/001154 to the same Applicant shows an apparatus wherein the device for turning up the end edge of the carcass ply about the bead core essentially comprises an annularly continuous pressure element axially movable toward/away to/from the forming support. Such pressure element comprises a plurality of arms, each one carrying a respective turning up roller at a free end thereof. The turning up rollers are arranged one next to the other in a circumferential direction and coaxially with respect to the longitudinal axis of the forming support. The rollers are radially movable in a synchronous manner, thus obtaining the radial expansion/contraction of the above pressure element between a contracted position and an expanded position. The combination of the radial movement of the turning up rollers and of the movement of such rollers toward/away to/from the forming support, allows turning up the end edge of the carcass ply around the bead core for making the tyre bead. The turning up device is further provided with means for adjusting the contracted position of the pressure element based on the radial dimension of the tyre to be made.